docs: def saturated_vapor_pressure(t_kelvin):
      """Saturated Vapor Pressure (Pa) at t_kelvin (K).
  
      This function accounts for the different behaviour above vs. below
      the freezing point of water.
  
      Note:
          [1] W. Wagner and A. Pru:" The IAPWS Formulation 1995 for the Thermodynamic
          Properties of Ordinary Water Substance for General and Scientific Use ",
          Journal of Physical and Chemical Reference Data,
          June 2002 ,Volume 31, Issue 2, pp. 387535
  
          [2] Vaisala. (2013) Humidity Conversion Formulas:
          Calculation Formulas for Humidity.
          www.vaisala.com/Vaisala%20Documents/Application%20notes/Humidity_Conversion_Formulas_B210973EN-F.pdf
      """
  
      if t_kelvin >= 273.15:
          # Calculate saturation vapor pressure above freezing
          sig = 1 - (t_kelvin / 647.096)
          sig_polynomial = (-7.85951783 * sig) + (1.84408259 * sig ** 1.5) + \
              (-11.7866487 * sig ** 3) + (22.6807411 * sig ** 3.5) + \
              (-15.9618719 * sig ** 4) + (1.80122502 * sig ** 7.5)
          crit_temp = 647.096 / t_kelvin
          exponent = crit_temp * sig_polynomial
          p_ws = math.exp(exponent) * 22064000
      else:
          # Calculate saturation vapor pressure below freezing
          theta = t_kelvin / 273.15
          exponent = -13.928169 * (1 - theta ** -1.5) + \
              34.707823 * (1 - theta ** -1.25)
          p_ws = math.exp(exponent) * 611.657
      return p_ws